Anionic Nanoclusters Research Articles

CHITOSAN / HEXAMOLYBDATE NANOSTRUCTURES FOR ORAL DRUG DELIVERY

Background: In recent decades, substantial progress has been achieved in the field of drug delivery through the creation of controlled-release formulations, leading to significant medical advancements. The primary objective of these controlled release systems is to sustain the desired drug concentration in the bloodstream or specific tissues for an extended duration. One class of nanostructures is polyoxometalates (POMs), which are negatively charged anionic nanoclusters consisting of metal and oxygen atoms. POMs are notable for their ability to be precisely controlled in size and shape. These characteristics, combined with their inherent negative charge, contribute to their stability and make them highly versatile structures. Aim: This study aimed to examine the self-assembly of organic-inorganic hybrids using polyoxometalate (POM) Lindqvist-type hexamolybdate and chitosan to synthesize novel 3D nanostructures. These nanostructures were then investigated for their suitability as nanocarriers for the chemotherapy drug )Temozolomide TMZ(. The release of TMZ from the nanocarrier was studied under various pH conditions. Methods: This study comprises two practical components. The first part focuses on synthesizing hierarchical nanostructures designed to load TMZ drugs. The amount of drug loaded onto the as-prepared nanostructure of POM-Chitosan was determined using High-Performance Liquid Chromatography (HPLC) at various loading times. The second part of the study investigates the release process of the TMZ drug from the hierarchical nanostructures. This release process is examined in two buffer solutions with distinct pH values. Results: The surface characteristics, size, chemical composition, and identity of the nanostructures were confirmed using techniques such as HPLC, FTIR, XRD, SEM, and XPS. The results confirm the successful complexation of chitosan with POM Lindqvist-type hexamolybdate. Discussion: The nanocarriers demonstrated an intriguing pH-dependent release behavior, suggesting their potential application in drug delivery systems. Conclusions: In this study, new nanocarriers of chitosan and POM were successfully prepared and loaded with TMZ (21% loading) via self-assembly for oral drug delivery. The as-prepared nanocarrier form of TMZ was fully characterized via XRD, FTIR, XPS, and SEM. The as-prepared oral form of TMZ showed an excellent pH-dependent release of TMZ, where the release rate at pH 7.4 was considerably faster than at pH 2.8.

Structural evolution and electronic properties of cerium doped germanium anionic nanocluster CeGen− (n = 5–17): Theoretical investigation

AbstractThe rare earth element doped germanium cluster represents a fundamental nanomaterial and exhibits potential in next‐generation industrial electronic nanodevices and applied semiconductors. Herein, the cerium‐doped germanium anionic nanocluster CeGen− (n = 5–17) has been comprehensively investigated by the double hybrid density functional theory of mPW2PLYP associated with the unbiased global searching technique of artificial bee colony algorithm. The cluster's growth pattern undergoes three stages: n = 5–9 with the replaced structure, n = 10–15 with the linked structure, and n ≥ 16 forming a Ce‐encapsulated in Ge inner cage motif. The clusters' PES, IR, and Raman spectra were simulated, and their HOMO‐LUMO gap, magnetism, charge transfer, and relative stability were predicted. These theoretical values can serve as a reference for future experiments to some extent. Moreover, the special D2d symmetry cage geometry of CeGe16− leads to a higher stability and preferred energy gap, making it an ideal candidate for further studies on its aromaticity, UV–vis spectra, and chemical bonding characteristics. In summary, CeGe16− has excellent optical activity that can be potentially employed as a building block in the development of optoelectronic functional materials.

The evolution of anionic nanoclusters at the electrode interface in water-in-salt electrolytes.

Water-in-salt electrolytes (WiSEs) have attracted extensive attention as promising alternatives to organic electrolytes. The limited electrochemical stability windows (ESWs) of aqueous electrolytes are significantly widened by WiSEs. However, the actual ESWs are lower than predicted as the interphase with WiSEs is not as stable as the solid electrolyte interphase (SEI) in conventional lithium-ion batteries. Therefore, identifying the interface state in WiSEs is vital to understanding their electrochemical behavior. Here, the structure of the lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) electrolyte near the interface of the carbon electrode (Ketjen black) was evaluated by experimental methods (neutron diffraction, Raman, and nuclear magnetic resonance spectroscopy) and molecular dynamics (MD) simulations. The results reveal that the introduction of carbon electrodes increases the size of the anionic nanoclusters and enhances the microphase separation at the interface. The MD simulations show that cation-π interactions are responsible for the evolution of anionic nanoclusters at the electrode interface. Moreover, lower charge transfer resistance is achieved at carbon-based electrodes due to the specific interface state. Our findings provide a strategy for introducing cation-π interactions between electrodes and electrolytes to improve the electrochemical performance.

Theoretical exploration of global minima, magnetism, structural stability and growth pattern of holmium‐doped silicon HoSin0/− (n = 10–18) nanoclusters

AbstractThe structural growth pattern of medium‐sized holmium‐doped silicon nanoclusters HoSin0/− (n = 10–18) was systematically probed by means of unbiased structure searches and double‐hybrid density functionals. The identified global minima of the nanoclusters have been confirmed by comparing the calculated spectral properties such as photoelectron spectroscopy, adiabatic electron affinities and vertical detachment energies with the experimental data. The structural evolution reveals Ho‐linked configuration for neutral and anionic nanoclusters (starting from n = 10 and 12, respectively). In this configuration, the linker Ho atom connects two small silicon sub‐clusters. The nanoclusters starting from n = 16 prefer the configuration in which Ho atoms reside in the center of Si‐cluster. The natural population analysis interprets the involvement of 4f electron of Ho atom in bonding. The participation in bonding has been traced by a transition of an electron from 4f to 5d orbital. This also results in larger magnetic moments (4 and 5 μB) than that of an isolated Ho atom. The HoSi16− nanocluster has good thermodynamic and moderate chemical stabilities as corroborated by average bond energy analysis, highest occupied molecular orbital‐lowest unoccupied molecular orbital gap, and chemical bonding, thus suggesting it the most appropriate building block for new functional nanomaterials.

Europium‐linked structures and electronic properties of nanosize semiconductor EuSin0/− (n = 11‐18) clusters

AbstractThe ground‐state structures of europium‐doped Si nanocluster and their anions EuSin0/− (n = 11‐18) are verified by using the ABCluster unbiased global search technique married with density functional theory methods and matching of simulated and experimental photoelectron spectroscopy. The results revealed that structural growth pattern for neutral and anionic nanoclusters is from Eu‐substitutional to Eu‐linked structure starting from n = 13 and 12, respectively. The natural population analysis showed that the 4f electrons of Eu atom in EuSin0/− (n = 11‐18) hardly participate in bonding, resulting the total magnetic moments are 7 and 8 μB, respectively. The highest occupied molecular orbital‐lowest unoccupied molecular orbital gap and average bond energies of EuSin0/− (n = 11‐18) have also been calculated respectively to examine their thermodynamic and chemical stability. The result showed that EuSi15 nanocluster possesses good thermodynamic and chemical stability, which may make it as the most suitable building blocks for novel functional nanomaterials.

Asymmetric Synthesis of Chiral Bimetallic [Ag28Cu12(SR)24]4- Nanoclusters via Ion Pairing.

In this work, a facile ion-pairing strategy for asymmetric synthesis of optically active negatively charged chiral metal nanoparticles using chiral ammonium cations is demonstrated. A new thiolated chiral three-concentric-shell cluster, [Ag28Cu12(SR)24]4-, was first synthesized as a racemic mixture and characterized by single-crystal X-ray structure determination. Mass spectrometric measurements revealed relatively strong ion-pairing interactions between the anionic nanocluster and ammonium cations. Inspired by this observation, the as-prepared racemic mixture was separated into enantiomers by employing chiral quaternary ammonium salts as chiral resolution agents. Subsequently, direct asymmetric synthesis of optically active enantiomers of [Ag28Cu12(SR)24]4- was achieved by using appropriate chiral ammonium cations (such as N-benzylcinchoninium vs N-benzylcinchonidinium) in the cluster synthesis. These simple strategies, ion-pairing enantioseparation and direct asymmetric synthesis using chiral counterions, may be of general use in preparing chiral metal nanoparticles.

Carbon Nanotubes as Electrically Active Nanoreactors for Multi-Step Inorganic Synthesis: Sequential Transformations of Molecules to Nanoclusters and Nanoclusters to Nanoribbons.

In organic synthesis, the composition and structure of products are predetermined by the reaction conditions; however, the synthesis of well-defined inorganic nanostructures often presents a significant challenge yielding nonstoichiometric or polymorphic products. In this study, confinement in the nanoscale cavities of single-walled carbon nanotubes (SWNTs) provides a new approach for multistep inorganic synthesis where sequential chemical transformations take place within the same nanotube. In the first step, SWNTs donate electrons to reactant iodine molecules (I2), transforming them to iodide anions (I(-)). These then react with metal hexacarbonyls (M(CO)6, M = Mo or W) in the next step, yielding anionic nanoclusters [M6I14](2-), the size and composition of which are strictly dictated by the nanotube cavity, as demonstrated by aberration-corrected high resolution transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. Atoms in the nanoclusters [M6I14](2-) are arranged in a perfect octahedral geometry and can engage in further chemical reactions within the nanotube, either reacting with each other leading to a new polymeric phase of molybdenum iodide [Mo6I12]n or with hydrogen sulfide gas giving rise to nanoribbons of molybdenum/tungsten disulfide [MS2]n in the third step of the synthesis. Electron microscopy measurements demonstrate that the products of the multistep inorganic transformations are precisely controlled by the SWNT nanoreactor with complementary Raman spectroscopy revealing the remarkable property of SWNTs to act as a reservoir of electrons during the chemical transformation. The electron transfer from the host nanotube to the reacting guest molecules is essential for stabilizing the anionic metal iodide nanoclusters and for their further transformation to metal disulfide nanoribbons synthesized in the nanotubes in high yield.

Structure and Stability of the Endohedrally Doped (X@CdiSi)i=4,9,12,15,16q=0,±1, X = Na, K, Cl, Br, Nanoclusters

Endohedral (X@CdiSi)q=0,±1 structures have been characterized by means of the density functional theory with X being alkali metals such as Na and K or halogens such as Cl and Br and with i = 4, 9, 12, 15, 16. These nanoclusters have been chosen because of their high sphericity, which is known to be one of the parameters determining the stability of the endohedral nanoclusters, along with the charge and size of the guest atom. In these structures, the atoms are trapped inside previously characterized spheroid hollow structures with positively charged Cd atoms and negatively charged S atoms. Moreover, although the radii of all atoms are similar, Cd atoms are located more inside the structure. For alkali metals, neutral and cationic endohedral compounds have been characterized and, for halogens, neutral and anionic nanoclusters have been characterized. It is observed that some of these guest atoms are trapped in the center of mass of the cluster, while others are found to be displaced from that center leadin...

Asymmetric Transformation of Monolayer-Protected Gold Nanoclusters via Chiral Phase Transfer

Phase transfer of aqueous racemic penicillamine-protected gold nanoclusters into chloroform is achieved by hydrophobizing the anionic nanocluster surface with a chiral ephedrinium cation (that is, chiral phase transfer), yielding asymmetric transformation or symmetry breaking of the optically inactive gold nanoclusters: The phase-transferred nanoclusters display appreciable optical activity in the metal-based electronic transition region. The ephedrinium cation contains chiral substituents with R,S absolute configuration, so that “nanocluster diastereomers” also can be produced via the phase transfer of enantiopure (S)- or (R)-penicillamine-protected gold nanoclusters with the chiral cations. Upon phase transfer, absorption spectra of the gold nanoclusters are almost invariant, whereas their circular dichroism (CD) signals exhibit a significant change in the metal-based electronic transition region. On the basis of the optical/chiroptical responses of the asymmetrically transformed gold nanoclusters as well as model quantum chemical calculations, the induced optical activity is most likely due to the ligand dissymmetric field brought about by the surface stereostructures.

Synthesis and structure of supramolecular polyoxothiometalate nanocluster containing 52 metal atoms [{Mo3S4(H2O)5}4(γ-SiW10O36)4]16–

The polyoxothiometalate complex [{Mo3S4(H2O)5}4(γ-SiW10O36)4]16– was prepared by the reaction of the cationic triangular molybdenum aqua complex [Mo3S4(H2O)9]4+ (electrophile) with the lacunary polyoxotungstate complex [γ-SiW10O36]8– (nucleophile). According to the results of single-crystal X-ray diffraction analysis of the dimethylammonium salt, the anionic nanocluster contains 52 molybdenum and tungsten atoms and has a cyclic porphyrin-like structure.